Remote control apparatus for electric motors



Filed March 18, 1939 5 Sheets-Sheet 1 xx X m&

May 20, 1947. A. P. DAVIS ETAL REMOTE CONTROL APPARATUS FOR ELECTRIC MOTORS 5 Sheets-$het 2 Filed March 18, 1939 May 20, 1947.

A. P. DAVIS ETAL REMOTE CONTROL APPARATUS FOR ELECTRIC MOTORS Filed March 18, 1959 5 Sheets-Sheet 3 May 20, 1947. A. P. DAVIS ETAL REMOTE CONTROL APPARATUS FOR ELECTRIOHOTORS 5 sheets sheet 4 Fil ed March 18, 1939 5 Shuts-Sheet 5 A. P. DAVIS ETAL Filed larch 18, 1939 REMOTE CONTROL APPARATUS FOR ELECTRIC MOTORS May 20, 1947.

MN w \h -ORN 5 ented May 20, 1947 REMOTE CONTROL APPARATUS FGR ELECTRIC MOTORS Arthur P. Davis, Stamford, Conn., and George Agins, Brooklyn, N. Y., assignors to The Arma Corporation, Brooklyn, N. Y., a corporation of New York Application March 18, 1939, Serial No. 262,766

19 Claims. (01. 172-239) felted.

All of the advantages of electronic follow-up control systems are realized in the system of the present invention while eliminating their disadvantages, to the end that a rugged, non-hunting system is provided, which is readily adaptable to various uses where it is desired to accurately and rapidly position one or more light or heavy controlled elements in accordance with the movements of a local or remote controlling element.

The control system of the present invention includes a reversing switching mechanism, one member of which is driven by a relatively low torque pilot motor controlled by the controlling element, and the other member of which is operatively connected to the drive motor whose acceleration should preferably be greater than that of the pilot motor, and which is controlled by the contacts of the reversing switching mechanism. The drive motor tends to de-energize itself by opening the contacts of the reversing switching mechanism. The direction of rotation, speed and acceleration of the drive motor are governed by the intermittent contact action of the reversing switching mechanism and by an automatically adjusted control auto transformer. The drive motor also drives the controlled ele ment, which accordingly instantaneously responds to all movements of the controlling element.

For a more complete understanding of the invention, reference may be had to the accompanying drawings, in" which:

Figure l is a schematic diagram of the control system of this invention adapted to three-phase alternating current operation, and illustrates the means for changing taps on the control auto transformer in response to speed changes of the drive motor;

Fig. 2 is a schematic diagram of the control system with modifications in the speed responsive means;

Fig. 3 is a schematic diagram of the control system with the reversing switching mechanism electrically connected in the rotor circuit of the drive motor;

Fig. 4 is a schematic diagram of a modifi arrangement for electrically connecting the con :trol auto transformer to the power supply;

Fig. 5 is a schematic diagram of the control system with a modified form or" device for ch" ing taps on the control auto transformer; and

Fig. 6 is a schematic diagram of the control system of this invention as adapted to single phase alternating current operation.

Referring to Fig. i oi the drawings, the core trolling element, located at a local or remote tion, may be a driven shaft [0, as shown, or other controlling device, which through gearing ii l2, actuates the rotors of respective high low speed self synchronous rotary induction transmitters i4 and 55. Located at the local or remote station of the controlled element, which may be a shaft I! connected to any heavy or light object for driving the same, are respective high and low speed self-synchronous rotary induction receivers l6 and Il, which are electrically connected respectively to the corresponding high and low speed transmitters I l and iii, so that the re-- tors of the receivers are in positional agreement with the rotors of the corresponding transmitters at all times. The two receivers ill and El are equipped with ollow-up heads is and iii, the contacts of which control a suitable pilot mo tor 40.

The two follow-up heads l8 and it include respective gears 20 and 2!, which are coaxially journalled to the ends of stationary sleeves 22 and 23, mounted on the frames of the respective receivers l6 and H. The shaft extensions 24 and 25 of their rotors are free to turn within the corresponding sleeves. The slip rings 26 and El, and trolley arrangements 28 and 29, are fastened. securely to the ends of the corresponding rotor shaft extensions 24 and 25 and are insulated from them. Two long contact segments till, 3i, and 32, 33, and two short contact segments, 3 35, and 36, 31, are mounted on the respective gears 20 and 2:, and insulated from them. and from each other. The two long segments are dia metrically opposite each other, and the two short segments are diametrically opposite each other and positioned in the spaces between the ends of the corresponding long segments. Contact rollers or brushes 38 and 39 are held at light pressure against the corresponding slip rings 26 and El at all times. A double trolley contactor 28 on high speed follow-up head l8, and a single trolley contactor 29 on low speed follow-up head i9, are

nsio. light pressure against the contact segments. The width of the double trolley 28 is h in relation to the length of the short segts it and 36 as to make the eflective gap on 1' side of its central position very short.

The 1ong segments of the two follow-up heads are electrically connected to the field systems of lot motor 40. The upper long segments 30 i are both connected to one field winding 45, and the lower long segments 32 and 33 are both connected to the other field winding 42. "foudensers 43, with protective resistance 44, are ally connected across the contacts of the follow-up heads for spark suppression. The pilot motor 40 is of the reversible type with its o field windings 4|, 42 independent, and the mechanical and electrical connections in the system are such that only one field winding can be energized at a time. When one field winding is energized, the pilot motor 40 will run in one tion, and when the other field winding is energized, it will run in the opposite direction.

The pilot motor shaft 45 carries gears 45 and "-ld mechanical filter 50. The mechanical tends to absorb irregularities in the system and may be of any well known type, such as that described in greater detail in copending apication Serial No. 115,488, filed December 12, Gear 48 drives gearing 48 to rotate gear oi hi h speed follow-up head 18, while gear 4! drives gearing 49 to rotate gear 2| of low speed follow-up head 19. The gear ratios and eledrical connections between pilot motor 40 and 3:: U i speed and low speed follow-up heads 18 and 19 are such that when a field winding of the pilot motor 40 is energized by a displacement of eys 28 and 29, gear 20 will be driven in the .1- e direction and through the same angle as made by trolley 28, while gear 2| will be driven in the same direction and through the same is as made by trolley 29. Therefore, when a a and 2! have turned through the same angles as their respective trolleys 28 and 29, the follow-up heads 18 and 19 will be in their neutral ons with the respective field of pilot motor energized, so that in effect, when the pilot motor is running it acts to de-energize itself by opening the contacts of the follow-up heads.

he output side of the mechanical filter 50 is ed to shaft which carries gears 52 and Gear 53 drives gear 54 which carries contact arm member 55 of reversing switching mechsm 58. Damping means, not shown, but prefbly of the type illustrated and described sa copending application, are interposed so tween gear 54 and contact arm 55. The reversing switching mechanism controls the power input "l direction of rotation of drive motor 51. contacts, 58 and 59, are mounted at the extremities of contact arm 55 and are insulated from the arm and from each other. Gear 80, lly mounted with gear 54, is free to turn idently of the latter and carries a disc insulating material upon which'are mounted two contacts 6i and 62, adapted to cooperate with co; ct 58, and two other contacts, 63 and 64,

ed to cooperate with contact 59.

In the disengaged position of the reversing switching mechanism 56, there is provided a air ap between contacts 58 and Si, 59 5 then there is between contacts 58 and 52, W and 84, as illustrated in exaggerated form in Fig. l. The contacts 6| to 64 are spring mounted, "p eferably as shown in said copending applicaso that when contact 58 engages contact 53, for example, and the transmitted gear 54 necessitates further turning of the arm 55, the spring of contact 5! will be compressed suiiiciently to allow contact 59 to engage 4 "lltact 64. Similarly, if gear 54 is turned ii; opposite direction with the same force, contact 59 will engage contact 53, and then contact 58 will engage contact 62. This is done to din v provide two steps of acceleration ier r 51. The first step of acceleration of drive motor 51 is split phase starting effected by condenser 55, which is electrically connected scros" phase of motor 65, and the I celeration step is produced by full stator voltage applied to the motor. Condensers 61 are connected across the contacts or the rev switching mechanism 58 for the purpo suppression. Further details of the construction of the reversing switch mechanism are illustrated and described in said ccpending applicant" motor 5! is a gear 68 which meshes with e...

, connections to drive 50 of reversing switching mechanism 56.

The ratio between gears 60 and 88, and the e' turning of the rotor gear 60 in the same directio same angle as made by gear 1, turned through t.- contacts of the revere s g ineche 56 will have returned to the disengaged position, thereby de-energizing drive motor 51, so that in effect, the drive motor in running tends to deenergize itself by opening 1 contacts oi reversing switching mechanism. The shaft ll of the drive motor 51 is the controlled element, and may be connected to any light or heavy t for the same In the usual forms of wound-rotor type mode tion motors equipped with slip rings and having external resist nces connected to the rotor "r torque speed control porno the rotor age and frequency are functions of the stator voltage and frequency, and the rotor slip. At zero rotor speed, th otor voltage and frequency a maximum. Fill the Y A voita 'e being equal to the ire voltage. At synchronous motor speed, the rotor voltage and frequency are zero. Torque is prozed the reaction 0 ti the stator field. especially at zero speed, sipated in the external rotor resistances is large, and this powe d in i; cour e rel cte vsta'toi power e these known characteristics and consic. tially of a three-phasestator Winding 66, and three-phase wo otor 12 equipp d in comp-in r. "T 1 am i a junction with the automatic adjusted auto transformer 13, provides means for obtaining drive motor speed-to combinations with relatively low power The electrical conned ions are such that the voltage produced in "re rotor 12 of the drive motor 5"! tends at all he volt. e which is applied to ti t. former l3, and the o ence between these two voltages is the effective voltage which causes the rotor current. At t r Les, the frequency the voltage produc rotor 12 is always the stator 66 voltage. posed in the circuit auto transformer 13,

approximately resistance that would be necessary for an vaient size wound rotor induction motor e uipped with slip rings; Therefore, for a reed, torque, although the same value of our will be supplied to the commutator equipped I? as would be supplied to the rotor of an equivalent size wound rotor induction motor equipped with slip rings, it will be supplied at a low effective voltage, so that the power dissi pated in the resistances 1'4 will also be low.

The auto transformer 13 consists essentially hree independent windings l5 and a movable arm iii secured to gear 93 so as to roate therewith, and being equipped with brushes i which make contact with the various windings ta windings l5, gear 93 and springs which secured to gear 533, are shown in Fig. 1 in ed form for purposes of clear illustration,

hut .i; will be understood that they preferably would be of circular construction.

The midof the idings are electrically conducted as shown, that when the Y connection is made, the transformer l3 will be in parallel with the stator winding lid of drive motor 51, i eby the primary of the auto transformer '1 ie under the control of the contacts of the reversing switching mechanism 56. Two Y-point tan and 80 are provided on windings l5, and the 1' noint selection and connection are directly the control of rotary type mechanical re y which is operated by the output of mechanical differential 82 for engagement with or set of the opposite contacts. Of the two tiai gear 83: is driven by gear 52 of pilot motor shaft 5|, and gear 84 is driven by gear 69 i the shaft of drive motor rotor '12.

I .i. the system is in operation, differential tends to drive the output of inc cal differential 82 in the direction oppothe controlling element I0 is again at rest the controlled element ll in positional cut with it, the mechanical relay 8! will the disengaged position with the contact midway between the two opposite sets lots. The mechanical relay 8!, and the per set of contacts before any of the re- Witching mechanism 56 contacts are tjiear 69, on the drive motor rotor 12 shaft, lso drives the input shaft 86 of the speed are .evice the auto transformer I3. The speed responsive device 81 consists essentially of a rotatable magnetic structure 88, a sectional view of which is shown in Fig. 1, comprising a magnetic field sys tern with multipoles which is mounted on shaft 56, so as to rotate therewith, and the poles of which are directed substantially radially. The i coils mounted on the poles, which may be four in number, are energized from a suitable direct current supply. Energization of the field co ls produces a radial field across the narrow gap between the poles faces and the flanged iron frame. Positioned in this air gap is a copper annulus 89, which is secured to shaft 90, so that the annulus rotates in the air gap about an axis al' bed with the axis of rotation of magnetic st ucture lit. As the magnetic structure rotates, eddy currents will be produced in the copper annulus, and these eddy currents react with the field. of the magnetic structure and tend to carry adapted to change taps on to that produced by input gear 83, so that the annulus around at. h magnetic structure. -For constant field strength, the voltage induced and the eddy currents thereby produced in the copper annulus 8d are roportional. to the speed of the magnetic structure therefore the de veloped torque of the copper annulus lid is proportional to the speed of the drive motor 51. The copper annulus dd is connected by shaft lid to pinion d2 driving raclr in suitable guides, not shown. Rack carries contact arm and its movement is restrained by opposed springs 9 l. Stops l l8 limit the movement of contact arm lti. With the linear restraining torque due to the springs 96, the movement of the contact arm id is accordingly proportional to the speed of drive motor iii.

In operation of the control system illustrated in Fig. and assuming that it is in its normal deenergized condition with the controlled element H in positional agreement with the controlling elernent id, rotation of the controllingelement will be transmitted through gearing l I and [2, to the rotors of the high and low speed transmitters M and IS. The resultant rotation of the rotors thereof in a corresponding direc tion and through the corresponding angle will result in an equal and substantially simultaneous movement of the rotors of respective high and low speed receivers l6 and it. The double trolley 2d of high speed -followup head it will accordingly be displaced to engage either segment 30 or segment 32, depending upon the direction of rotation of the controlling element Hi. This will effect energization of the appropriate held coil. or 42 of pilot motor and. cause the pilot motor to rotate gears 20 and 2% in the appropriate direction, until the iollow up heads it and is are again in the neutral position.

rotation of the pilot motor till also be transmitted by its shaft 45 through mechanical filter 58, to gears 52 and 53. The rotation of gear 52 will be transmitted to the input gear 83 of mechanical differential and the output of the mechanical differential will actuate the contact plate of mechanical relay 8 l, and thereby conmeet the appropriate taps, either "is or iii], of the three windings iii or auto transformer r relation. The rotation of gear 53 by pilot motor 40 will be transmitted through gear 54 to actuate contact arm 55 of reversing switching mechanism Depending on the direction of rotation of the controlling element iii, the appropriate contact on contact arm 55 will engage the cooperating contact, either til or which will effect split phase operation of c motor ill and also auto transformer in the manner escribed. When the speed responsive device 81 is at rest, the brushes I? will rest at the midpoint iii of auto transformer so that split phase operation of the drive motor and auto transformer will cause the drive motor 51 to start.

If split phase operation does not cause the drive motor iii to accelerate quickly enough to follow rapid movements oi the controlling element Hi, the pilot motor 40 will impart additional movement to the contact arm 555 of reversing switching mechanism 56, so that the other contact oncontact arm 55 will engage cooperating contact 64 or 62, and thereby provide full phase operation to the drive motor 51 and auto transformer 13. Rotation of the drive motor 57 operates the speed responsive device 8i, so that th brushes ll will be driven away from the midpoint 18 of auto transformer windings 15 toward the Y-point which previously was selected and connected by the operation of mechanical relay 8! in response the direction of movement of the controlling e'iernent l0, and through a distance which is proportional to the speed of the drive motor 51, and thereby reduce a proportional amount the voltages that are applied to the rotor 12 of the drive motor by the auto transformer 13.

As the speed of the drive motor 51 increases, the voltage produced in its rotor 12 will decrease a proportional amount. The taps on the auto transformer may be arranged in such relationship to the brushes 11 on contact arm 16, that, for example, the effective voltage in the rotor circuit of drive motor 51 will be a, substantially constant value for increasing motor speeds, or, alternatively, the taps may be arranged so that the effective voltage will increase or decrease with in creasing motor speeds. The effective voltage in the circuit of the rotor 12 of drive motor 51 can therefore be controlled and regulated in response to the speed of the drive motor, and in accordance with predetermined torque requirements which are met by the selection of the auto transformer, so that the voltage between taps varies in any desired or required manner. The drive motor will quickly accelerate so that the controlled element 1i will be driven into positional agreement with the controlling element l0. As the drive motor slows down in response to slowing of the controlling element 10, the torque produced by the speed responsive device 81 will be reduced an amount proportional to the decrease in drive motor 51 speed, and the restoring force of the restraining springs 9| will tend to move the contact arm 16 of the auto transformer 13 toward the midpoint 18, until a balance is reached between the force of the springs 9| and the torque of the speed responsive device 81.

For any sudden slowing, stopping, or reversing of the controlling element 10, the drive motor will quickly turn the contact gear 60 of the reversing switching mechanism 56 from the position that determines operation of the drive motor 51 in one direction, through the neutral or zero speed position, to the position for operation of the drive motor 51 in the opposite direction. The mechanical relay 8! is substantially instantaneously reversed, So that the Y-point of the auto transformer 13 will be changed from one side of the midpoint 18 to the other side. Inasmuch as the drive motor 51 and the controlled element 1|, due to their kinetic energy, are still turning in the original direction when the sudden deceleration of the controlling element takes place, and the phase sequence of the voltage applied to the drive motor stator and the primary of the auto transformer has been reversed by the contacts of the reversing switching mechanism, the reversing of the Y point of the auto transformer, with the position of the contact arm 16 unchanged, will cause the voltage across the secondary of the auto transformer to instantaneously increase, and also causes the voltage which is produced in the drive motor rotor 12 to increase and be equal to the standstill rotor voltage, plus the rotor speed voltage. Therefore, retarding torque will be produced in the drive motor 51, with the kinetic energy of the drive motor and controlled element causing power to be returned to supply,

Also, inasmuch as the device 81 for changing taps on the auto transformer 13 is responsive to the speed and direction of rotation of the drive motor 51, the application of the regenerative braking to the rotor of the drive motor will cause the contact arm of the auto transformer to move toward the new Y-point and thereby decrease the secondary voltage of the auto transformer.

The braking of the drive motor rotor 12 also creases the voltage which is produced in the rotor. The retarding torque of the rotor will continue effective until the rotor slows down to the required speed, in the case of sudden slowing of the controlling element In, or until the rotor slows to zero speed, in the case of stopping or reversing of the controlling element I 0. When zero speed of the drive motor is obtained, the contact brushes 11 will be at the midpoint 18 of the auto transformer windings. From this point on, in the case of reversing of the controlling element, the drive motor will accelerate to the required speed in the reverse direction of rotation, in the same manner as heretofore described. Therefore, the controlled element 1| will substantially instantaneously respond to all movements of the controlling element l0, so that the elements will at all times be in positional agree ment with each other.

up head l8 from the circuit, so that the high speed follow-up head l8 will be deprived of control and control will be assumed by low speed follow-up head l9. When angular correspondence between elements I0 and 1| is again approximated, trolley 29 will again move into en gagement with segment 35, so as to restore control to high speed follow-up head 18.

In the control system of this invention, the speed of the drive motor is not limited to the synchronous speed as is the case in the usual type of wound rotor induction motors equipped with slip rings. This synchronous speed will be exceeded when the brushes 11 pass the connected Y-point taps 19 or B0 in a direction away from the midpoint 18 toward the end of the trans-- former windings 15.

Where a large auto transformer is necessary, and the torque produced by the speed responsive device 81 is not sufficient to change the taps on the auto transformer, a torque amplifier of suit able power, consisting of a follow-up head and motor similar to follow-up head 18 and pilot motor 40, may be added to the control system by interposing the follow-up head between gear 93 and contact arm 16, so that gear 93 will drive the double trolley of the follow-up head, and the contact arm of ihe auto transformer will be driven by the large gear of the followup head.

The arrangement of Fig. 2 illustrates a modification of the speed responsive means for changing taps on the auto transformer 13 of the ar-- rangement of Fig. l, with the other parts identi' cal and therefore not illustrated. This speeci responsive means consists essentially of a relatively small alternatihg current commutator control motor 94, which has a main field winding and an auxiliary, distributed field winding 96. The auxiliary field winding 96 is connected in quadrature with the main field winding 95, and both the main and auxiliary field windings of the control motor 94 are electrically connected to the auto transformer winding 15, which is directly connected to the power line, the main field winding 95 being connected to midpoint 18 and Y- point location 19, so that in operation the main field strength will remain constant. The auxiliary field winding 96 is connected to midpoint 18 and to mechanical relay contact plate 85, so that in operation the auxiliary field winding 98 will be connected across the selected primary of to the drive motor stator 66, the auto transformer 13, and. the control motor 94. In response to the intermittent contact action of the reversing switching mechanism 56, the drive motor 51 will accelerate, and at the same time the speed responsive means for changing taps on the auto transformer will operate. In this operation, when the effective voltage in the drive motor 51 rotor circuit becomes smaller than a predetermined value, the voltage induced in the armature of the control motor 94 by the auxiliary field winding 96 will be greater than the opposing voltage across the series resistor 14, so that the torque produced by the control motor 94 will be in a direction which tends to drive the contact arm 16 of the auto transformer so that the voltage applied to the drive motor rotor will increase the effective voltage to its former predetermined value.

Conversely, when the effective voltage in the drive motor 51 rotor circuit becomes greater than the predetermined value, the voltage induced in the armature of the control motor 94 by the auxil iary field winding 96 will be smaller than the op posing voltage across the series resistor 14, so that the torque produced by the control motor 94 will be in a direction which tends to drive the contact arm 16 of the auto transformer 13, whereby the voltage applied to the drive motor rotor will crease the effective voltage to its former predator mined value. VVhED. the effective voltage in the drive motor 51 rotor circuit is equal to the predetermined value, the voltage induced in the armature of the control motor 94 by the auxiliary field winding 96 will be equal to the opposing voltage across the series resistor 14, so that the control motor 94 will be at rest along with the contact arm 16 of the auto transformer 13.

As the drive motor 51 accelerates, the voltage produced in its rotor 12 will decrease, thereby decreasing the effective voltage in the rotor cir cult, so that the to produced by the control motor 94 will drive e contact arm 16 of the auto transformer 13 away frcm the midpoint in a direction determined by the direction of movement of the controlling element l0. and thereby decrease the voltage applied to the drive motor rotor 12. The control motor 9 is therefore re sponsive to the speed of the drive motor 51, and when the drive motor has accelerated to the required speed, both the voltage produced in the rotor 12 of the drive motor 51 and the voltage applied to the rotor 12 by the auto transformer The effective voltvoltage s, will then be the predetermined v which causes the control motor 94 to be at rest will be at unchanging values. age, which is the difference between these along with the contact arm '16 of the auto transformer 13.

If the controlling element I0 is then suddenly reversed in direction, the Y-point of the auto transformer 13 will be substantially instantaneously reversed, and also the phase sequence of the voltage to the drive motor stator '66 and primary of the auto transformer will be. reversed. This will reverse the main field of the control motor 94 with respect to both the auxiliary field and armature. Regenerative braking of the drive motor 51 will occur, and the control motor 94, by virtue of the reversed main field 95, will drive the contact arm 16 of the auto transformer toward the midpoint. The contact brushes 11 will be at the midpoint of the auto transformer when the drive motor 51 is at zero speed, and the drive motor 51 will then accelerate in the reverse direction of rotation.

98 and 99 will engage their respective cooperatest of ing contacts before contact arm I09 engages its corresponding cooperating contact. This provides two steps of acceleration for the drive motor 51. The windings 15 of auto transformer 13 are permanently connected in Y relation at location 19. The contact arm 16 of the auto transformer is provided with two spaced contact brushes I01, I02, for each winding. These brushes spaced a predetermined distance apart in a fixed position on the contact arm 16, and are insulated from thecontact arm and from each other. The remainder of the system is the same as th of 1 and is not illustrated in the inter!- simplicity.

operation of the arrangement of Fig. 3, upon tting, the contact arm it of the auto transrcrmer 13 wii} the midpoint, so that both contact hrusi 1rd I92 will be spaced an equal distance midpoint 18, while voltage will be appli the power service to the stator windings oi the drive motor 51 and the primary windings of the auto transformer 13. Upon engagement of the contactsoi the reversin switching mechanism 91, the secondary of the auto transformer .3 will apply a voltage to the rotor 12 oi the drive motor 51. The drive motor 51 will accelerate, and the speed-responsive. device 81, adapted for changing taps on the auto transformer 13, will drive the contact arm 16 away from the midpoint in a direction determined by the direction of movement of the controlling element 10. When the excitation of the stator field 66 and rotor 12 of the drive motor 52 are rotating in the same direction, the contact 1B of the auto transformer will be driven toward the Y-point. which will decrease the voltage which is applied to the drive motor rotor 12 by the auto transformer, but when the stator field excitation and rotor of the drive motor 51 are rotating in opposite directions, the contact arm 16 or" the auto transformer will be driven away from the Y-point, which will increase the voltage a if) transformer 13. The effective voltage in the drive motor 51 rotor circuit will therefore be controlled and regulated in response to the speed of the drive motor 51, and when the required speed is reached, the contact arm 16 of the auto transformer will be at rest with the contact brushes on the correct setting.

If the motion of the controlling element I is suddenly reversed in direction, the contact member 96, 98, I00 of the reversing switching mechanism 91 will engage the opposite cooperating contacts, so that the control will be switched to the brushes on the contact arm 16 that are closest to the midpoint of the auto transformer 13. This will instantaneously increase the voltage which is applied to the drive motor rotor 12 by the auto transformer 13 when the contact arm 16 is between the midpoint and the Y-point, or will instantaneously decrease the voltage which is applied to the drive motor by the auto transformer when the contact arm 16 is at the other side of the midpoint, and with the kinetic energy of the drive motor 51 and controlled element I0, will cause regeneration braking of the drive motor 51. Braking of the drive motor will decrease the torque of the speed responsive device 61 for changing taps on the auto transformer 13 and thus allow the force of the restraining springs SI to drive the contact arm 16 of the auto transformer toward the midpoint to increase or decrease the voltage applied to the drive motor rotor 12 by the auto transformer 13 a proportional amount, so that zero speed will be quickly reached. When zero speed of the drive motor 51 is reached, the contact arm 16 of the auto transformer will again be in the starting position, i. e., the midpoint of the auto transformer will be equidistant between the contact brushes IOI, I02. The drive motor 51 will then quickly accelerate in the opposite direction until the controlled element H is again in positional agreement with the controlling element. In this modification, the contacts of the reversing switching mechanism 31 are required to handle the drive motor rotor current, which is much higher than the stator current handled by the contacts in the arrangement of Fig. 1, for example.

Fig. 4 illustrates a modification of the arrangement of Fig. 1 in respect to connections of the auto transformer to power, the remainder of the arrangement of Fig. 1 remaining the same. In the modification of Fig. 4, instead of being supplied directly from the powerservice which supplies the drive motor stator the auto transformer 13 is supplied from a portion of the drive motor stator windings 66, so that the latter act as an auto transformer. Tapped connections in the stator-transformer 66, corresponding to the desired voltage, supply the control auto transformer 13. The rotor 12 of the drive motor 51 is wound accordingly, and this method is preferred in cases where excessively high voltages would be induced in the secondary of the control auto transformer 13 if it were connected directly to the power service. i

Fig. illustrates a modification of the auto transformer 13 control of the arrangement illustrated in Fig. 1, in which the stator windings of a relatively small torque motor I 03 are connected in delta relation to each other and in parallel with the stator windings 66 of the drive motor 51. Working in conjunction with torque motor I03 is a preloaded spring device I04, which consists essentially of two spiral springs I05 and I06 with the inner end of each spring fixed to stationary rod I01 and their outer ends engage fixed stops I06. A crank bail I09 secured on the motor shaft carries fingers H0 and III, and the other end of the motor shaft carries pinion 92 meshing with rack 93. Spring I06 is wound in the opposite direction to spring I05 and both springs are preloaded an equal amount, and are prevented from unwinding by means of the fixed stops I06. In one direction of rotation of bail I06, spring I05 only will be additionally wound by corresponding finger I I0, and in the opposite direction of rotation of bail I09, spring I06 only will be additionally wound by finger III. Due to the preloading, the initial tension of the springs I05 and I06 is large compared to the additional tension required for operation, so that the restoring force of the springs I 05 and I06 acting on the ball ,1 09 will be approximately constant for all positions of the auto transformer contact arm 16, except for the zero speed position where the springs I05 and I06 engage stops I06 and this restoring force will be zero. This arrangement of Fig. 5 for changing taps on the auto transformer 13 tends to adjust itself, so that when the drive motor 51 is running, the ratio of the engaged time to the disengaged time of the reversing switching mechanism 56 contact action will be constant for all constant speed and torque conditions, independent of the speed or torque of the drive motor 51.

Thus, upon starting, the contact arm 16 of the auto transformer 13 will be at the midpoint, and upon engagement of the contacts of the reversing switching mechanism 56, voltage will be applied to the drive motor 51 stator 66, the torque motor I03 stator, and the auto transformer 13. In response to the intermittent contact action of the reversing switching mechanism 56, the drive motor 51 tends to accelerate to the required speed determined by the movement of the controlling element I0.

Inasmuch as the stator windings of both the drive motor 51 and torque motor I03 are energized simultaneously by the contacts of the re versing switching mechanism 56, any torque or speed requirements imposed on the drive motor 51 will also be reflected in the operation of the torque motor I03. For example, if during the operation of the system, additional speed or torque is required from the drive motor 51, the ratio of the engaged time to the disengaged time of the reversing switching mechanism 56 contact action will increase. This action will increase the average value of the voltage that is applied to the stators of the drive motor 51 and the torque motor I03, which will increase the torque of the torque motor I03 and cause it to drive the contact arm 16 of the auto transformer 13 away from the midpoint in a direction determined by the direction of movement of the controlling element I0 Movement of the contact arm 16 of the auto transformer away from the midpoint will decrease the voltage that is applied to the drive motor 51 rotor by the auto transformer 13, and therefore the effective voltage and the current in the drive motor rotor 12 circuit will increase, and a corresponding increase in torque and speed will be obtained.

When the required speed or torque is reached by the drive motor 51, the ratio of the engaged 7 time to the disengaged time of the reversing the torque produced by the torque motor I03 to a value equal in force but opposite in sense to the restoring force of the spring device Hi4, so that the resultant force acting upon the contact arm 16 of the auto transformer 13 will be zero, and therefore the contact arm '16 will remain at this setting until the torque motor is affected by changes in the contact action oi the reversing switching mechanism 56. For any sudden slowing, stopping, or reversing of the controlling element l0, regenerative braking of the drive motor 51 will occur, and when the controlling element I is again at rest with the controlled element H in positional agreement with it, the contact arm 16 of the auto transformer '13 will be at the midpoint.

Fig. 6 illustrates schematically the control systern of this invention as adapted to the use of a single phase drive motor, the remainder of the system being the same as illustrated in Fig. 1. The drive motor H2 in this case is preferably of the single phase commutator alternating current type, having a main field winding H3, an auxiliary field Winding H4, and armature H5. A resistor H6 is interposed in the circuit between the auxiliary field winding H4 and one of the contacts on the arm of the reversing switching mechanism 56, so that two steps .of acceleration for the drive motor H2 are obtained. The auto transformer H1 is of single phase-type, and the contact arm 16 is equipped with two spaced contact brushes HH and 102, so spaced and insulated from each other that a predetermined voltage will exist between the brushes when the transformer H1 is energized.

Upon starting, the contact arm of the auto transformer H1 will be at the midpoint, so that both contact brushes will be spaced an equal distance from the midpoint, and voltage will be applied directly to the main field winding H3 of the drive motor H2, and to the primary of the auto transformer H1. Upon engagement of the contacts of the reversing switching mechanism 56, the initially displaced position of the brushes on the contact arm 16 with respect to the midpoint of the auto transformer, will cause the secondary of the auto transformer Hl to apply a voltage to the auxiliary field winding H4 of the drive motor. The contacts of the reversing switching mechanism 56 first engaged, contact 58 with either contact Si or 62, will apply reduced voltage to the auxiliary field winding H4 due to the resistor H6 interposed in the circuit. The contacts of the reversing switching mechanism brush on the contact arm 16 of the auto transformer H1. This reduces the voltage that is applied to the auxiliary field winding H4 of the drive motor H2, and with the kinetic en rgy. of the drive motor H2 and controlling element ID, will cause regenerative braking of the drive motor H2. Braking of the drive motor H2 will reduce the torque of the speed responsive device 87 for changing taps on the auto transformer H1, and thus allow the restraining springs 9| to drive the contact arm 76 of the auto transformer toward the midpoint, thereby reducing the voltage applied to the auxiliary field winding H4 by a proportional amount so, that zero speed will be quickly reached. When zero speed is reached, the contact arm 16 of the auto transformer will again be in the starting position with the midpoint of the auto transformer equidistant between the two contact brushes. The drive motor H2 then accelerates in the opposite direction until the controlled element H is again in positional agreement with the controlling element l0.

Although certain preferred embodiments of the invention have been illustrated and described herein, the invention is not to be limited thereby. but is susceptible of various changes in fonm and detail within the scope of the appended. claims.

We claim:

1. In. a system for controlling a controlled element with a controlling element, the combination of a driving motor for said controlled element, a reversing switch for controlling said motor and jointly operated thereby and by said controlling element, and an auto transformer in the supply circuit of said motor responsive to 56 next engaged will short circuit the resistor I I6 and apply the auto transformer secondary voltage, as determined by the position of the contact arm, to the drive motor auxiliary field winding H4,

The drive motor H2 will accelerate, and the speed responsive device 1 for changing taps on the auto transformer H! drives the contact arm 16 away from the midpoint in a direction determined by the direction of movement of the controlling element l0, and thus increases the voltage applied to the auxiliary field winding i [4 of the drive motor H2. Inasmuch as the device 1 for changing taps on the auto transformer H1 is responsive to the speed of the drive motor H2, when the required speed is reached the contact arm 16 will be stationary with the contact brushes on the correct setting.

If the controlling element 10 is then suddenly reversed, the contact arm member of the reversing switching mechanism 56 will engage the opposite contacts, so that the control will be substantially instantaneously switched to the other the movement of said motor for controlling the voltage of the supply thereto.

2. In a system for controlling a controlled element with a controlling element, the combination of a reversible driving motor for said controlled element, a reversing switch controlling said motor" and having two sets of cooperating movable contacts, driving connections between one set of contacts and said motor, operative connections between said controlling element and said other set of contacts, and an auto transformer responsive to movement of one of said elements for controlling said motor independently of said switch.

3. In a system for controlling a controlled element with a controlling element, the combination of a reversible driving motor for said controlled element, a reversing switch controlling said motor and having two setsof cooperating movable contacts, driving connections between one set of contacts and said motor, operative connections between said controlling element and said other set of contacts, and electrical means responsive to the speed of one of said elements for controlling said motor independently of said switch.

4. In a system for controlling a controlled element with a controlling element, the combination of a reversible driving motor for said controlled element, a reversing switch controlling said motor and having two sets of cooperating movable contacts, driving connections between one set of contacts and said motor, operative connections between said controlling element and said other set of contacts, a transformer for said motor, and means responsive to movement of one of said eleanents for changing supply connections to said transformer.

5. In a system for controlling a controlled element with a controlling element, the combination of a reversible driving motor for said controlled element, a'reversing switch controlling said motor and having two sets of cooperating movable contacts, driving connectionsbetween one set of contacts and said motor, operative connections between said controlling element and said other set of contacts, and an auto transformer in the circuit of said motor controlled by one of said elements.

6. In a system for controlling a controlled element with a controlling element, the combination of a reversible driving motor for said controlled element, a reversing switch controlling said motor and having two sets of cooperating movable contacts, driving connections between one set of contacts and said motor, operative connections between said controlling element and said other set of contacts, and an auto transformer in the circuit of said motor resmnsive to the movement of said motor.

'7. In a system for controlling a controlled element with a controllin element, the combination of a reversible driving motor for said controlled element, a reversing switch contr iling said motof and having two sets of cooperating movable contacts, driving connections between one set of contacts and said motor, operative connections between said controlling element and said other set of contacts, an auto transformer in the circult of said motor, and means responsive to the speed of one of said elements for controlling said transformer.

8. In a system for controlling a controlled element with a controlling element, the combination of a reversible driving motor for said controlled element, a reversing switch controlling said motor and havin two sets of cooperating movable con tacts, driving connections between one set of contacts and said motor, operative connections between said controlling element and said other set of contacts, an auto transformer in the circult of said motor, and means respor speed or" said driven element for contr l transformer.

9. In a system for controlling controlled elee it with a controlline element, the combina- -i of a. reversible dllvlllg' motor for said con "rolled element, a reversing switch controlling said motor and having two sets of cooperating movable contacts, driving connections between one set of contacts and said motor, operative connections between said controlling element and said other set of contacts, an auto transformer for said motor, means responsive to movement of one of said elements for controlling said transformer, and means responsive to movement of one of said elements for changing supply connec tions to said transformer.

10. In a system for controlling a controlled element with a controlling element, the combination of a reversible driving motor for said controlled element, a reversing switch controlling said motor and having two sets of cooperating movable contacts, driving connections between one set of contacts and said motor, operative connections between said controlling element and said other set of contacts, an auto transformer for said motor, a movable contactor therefor, and means responsive to movement of one of elements for controllin said contact-or.

11. In a system for controlling a controlled element with a controlling element, the co nbina tion of a reversible driving motor for s trolled element, a reversing switch CU'ZtIf said motor and having two sets or ccopera one set of contacts and said motor, operative connections between said controlling element and said other set of contacts, an auto transformer for said motor controlled by movement of one of said elements, and means responsive to stopping of said one element for restoring said transformer to neutral position.

12. In a system for controlling a controlled element with a controlling element, the combination of a reversible driving motor for said controlled element, a reversing switch controlling the field excitation of said motor and having two sets of cooperating movable contacts, driving connections between one set of contacts and the rotor of said motor, operative connections between said controlling element and said other set of contacts, and an auto transformer actuated by the rotor of said motor for controlling said rotor.

13. In a system for controlling a controlled element with a controlling element, the combination of a reversible driving motor fo said controlled element, a reversing switch controlling said motor and having two sets of cooperating movable contacts, driving connections between one at of contacts and said motor, operative conns between said controlling element and said other set of contacts, an auto transformer for said motor, a contactor therefor, means responsive to the speed of said motor for actuating said contactor, and means responsive to a reversal in the direction of rotation of said motor for changing the supply connections to said transformer.

14. In a system for controlling; a controlled element with a controlling element, the combination of a reversible driving motor for said controlled element, a reversing switch controlling said motor and having two sets of cooperating movable contacts, driving connections oetween one set of con tacts and said motor, operative connections between said controlling elemen and said'other set of contact an auto transformer for said nary motor energized in accordon of said first motor, and said auxiliary .j. In a system 1:)! controhlng a controlled element with r controlling element, the combination of ie driving motor for said controlled element, versing switch having two sets of cooperating movable contacts, driving connections between one set of contacts and said motor, operative connections between said controlling elernent and said other set of contacts, electrical connections between one set of contacts and said motor, electrical connections between the other set of said contacts and supply, an auto transformer in said first-named electrical connections, and operative connections between said motor said auto transformer.

16. In a system for controlling a controlled elent roll a controlling element, the combination rsible driving motor for said controlled "em, reversing switch having two sets of ooperatin movable contacts, driving connections oetween one t of contacts and said motor, operative connections between said controlling element and said other set of contacts, electrical onecticns between one set of contacts and said motor, electrical connections between the other aid contacts and supply, an auto transwnained electrical connections, the speed of rotation of said 17 motor, and operative connections between said means and said auto transformer.

17. In a system for controlling a controlled element with a controlling element, the combination of a driving motor for said controlled element, a transformer wound stator for said motor connected to supply, an auto transformer supplied from said stator, variable connections between said auto transformer and the rotor of said motor, and means responsive to the speed of the rotor of said motor for adjusting said variable connections.

18. In a system for controlling a controlled element with a controlling element, the combination of a reversible driving motor for said controlled element, a reversing switch controlling the field excitation of said motor and having two sets of cooperating movable contacts, driving connections between one set of contacts and the rotor of said motor, operative connections between said controlling element and said other set of contacts, an auto transformer, connections between said transformer and rotor circuit whereby the transformer voltage opposes the rotor voltage, and operative connections between the rotor and said transformer, whereby the rotor circuit is adjusted in accordance with the mechanical output of said motor.

19. In a system for controlling a, controlled '18 element with a controlling element. the combination of a driving motor for said controlled element, a reversing switch for controlling said motor and jointly operated thereby and by said controlling element, an auto transformer in the rotor circuit of said motor, an auxiliary motor in the stator circuit of said driving motor, 0perative connections between said auxiliary motor and said auto transformer, and means responsive to the direction of rotation of said auxiliary motor for restoring said transformer to neutral position upon stopping of the movement of said controlled element.

AR'I'HUR P. DAVIS. GEORGE AGINS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED ST TES PATENTS Y Number Name Date 1,950,427 Willink Mar. 13, 1934 935,327 Routin Sept. 28, 1909 FOREIGN PATENTS Number Country Date 683,021 France Feb. 22, 1929 Certificate of Correction Patent No. 2,420,817. May 20, 1947.

ARTHUR P. DAVIS ET AL.

It is hereby certified that the name of the assignee in the above numbered patent was erroneously described and specified as The Anna Corporation Whereas said name should have been described and specified as Armo Corporation, as shown by the record of assignments in this Office and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Signed and sealed this 26th day of August, A. D. 1947.

[SEAL] LESLIE FRAZER,

First Assistant C'ommissioner of Patents.

AAA HAA AA AAAH MA M Certificate of Correction Patent No. 2,420,817. May 20, 1947.

ARTHUR P. DAVIS ET AL.

Itiis hereby certified that the name of the assignee in the above numbered patent was erroneously described and specified as The Arma Corporation Whereas said name s ouldiheve been described and specified as Arma Corporation, as shown by the record of assignments in this Office; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Signed and sealed this 26th day of August, A. D. 1947.

[SEAL] I LESLIE FRAZER,

First Assistant aommz'ssz'oner of Patents. 

